A tungsten electrode such as used in tungsten-inert-gas (TIG) welding must be very accurately shaped for best welding results, in particular when used in a computer-controlled process. The working end of the electrode must be ground to a point. More specifically the tip must be nearly perfectly conical with a cone axis corresponding to the longitudinal axis of the electrode rod, and the scratches formed by the grinding must radiate from the point, not run skew or transversely.
Hence such an electrode rod is shaped by engagement with a grinding disk with the electrode axis wholly skew, that is in no way perpendicular or parallel, to the rotation axis of the disk which itself is perpendicular to the grinding face of the disk. Thus seen parallel to the disk axis the rod axis is a secant, and the rod axis also forms an acute angle with the plane of the disk face.
The machine for doing this grinding normally has, in addition to the disk and its rotary drive, a holder for the electrode. This holder can pivot about an axis perpendicular to the disk axis and parallel to its face, and the electrode can be rotated in this holder about its own axis. To this end the electrode is held somewhat back of the point to be ground in a chuck- or collet-like device that itself is supported adjacent the grinding disk and that itself can be rotated about the necessary skew axis.
The tungsten electrode is typically sintered so that it is not perfectly straight and uniform. In addition the rod forming the electrode is frequently made in long pieces that are then subdivided longitudinally into individual electrodes. Thus when a particularly curved piece is chucked in the holder and ground, the point formed on the electrode will not lie on the center of the electrode but instead will lie on an extension of the axis of the part of the workpiece where it is held. This problem is aggravated when the electrode is held relatively far from its tip. These problems are present in systems wherein the electrode rod is loosely received in the holder and is guided by hand therein.